Compare 2.5-3.5" HDD Pins

N.B.
All the information in this page is intended only for guidance. It is believed to be correct and not everyone adheres to standards. The information is used at your own risk.

40-pin IDE/ATA Connections for 3.5" Desktop Hard Drives

Fig 1. Female slots

Fig 2. Male pins

Note:

1. Pin/Slot 20 (arrowed above) may have
an absent pin or be blanked of as a key identifier. It carries no data nor
power.

2. The outside notch beside Pins/Slots 19
and 21 may or may not be present.

3. The ribbon cable normally has a red
line going to Pin/Slot 1.

44-pin IDE/ATA Connections for 2.5" Laptop Hard Drives

Fig 3. Female Slots

Fig 4. Male Pins

The first 40 are the same as their desktop cousins but there are an
additional four pins (41 to 44) which use 5V power normally carried by a
molex connector on a desktop hard drive.

Don't confuse the four pins (41 to 44) with another bank of four pins (-
usually separated from the other 44 pins by a gap -) which are for jumpering
the laptop hard drive. These are usually not jumpered at all on laptop hard
drives.

Complete end-view of 2.5" Hard Drive (inc. 4-pin jumper block)

Fig 5. End-view of 2.5" drive - (PCB on top here).

The four-pin jumper block seldom actually has any jumpers on it and this
is commonly the Master setting. There is however much variation and the drive
itself should be examined carefully for the correct jumper settings or the
internet browsed for supporting documentation for the make and model in
question.

Dont confuse the above layout with the less commonly seen 60-pin blocks,
where the first six pins are customisable and the last 44 are the same as the
44-pin ATA/Power layout as in Fig 5. The absent pin (if it is absent) for Key
at posn 20 can often be very useful in orientation.

The ATA Pin-Outs consist of:

Pin

Name

Dir

Description

1

/RESET

OUT

Reset

2

GND

------

Ground

3

DD7

IN/OUT

Data 7

4

DD8

IN/OUT

Data 8

5

DD6

IN/OUT

Data 6

6

DD9

IN/OUT

Data 9

7

DD5

IN/OUT

Data 5

8

DD10

IN/OUT

Data 10

9

DD4

IN/OUT

Data 4

10

DD11

IN/OUT

Data 11

11

DD3

IN/OUT

Data 3

12

DD12

IN/OUT

Data 12

13

DD2

IN/OUT

Data 2

14

DD13

IN/OUT

Data 13

15

DD1

IN/OUT

Data 1

16

DD14

IN/OUT

Data 14

17

DD0

IN/OUT

Data 0

18

DD15

IN/OUT

Data 15

19

GND

------

Ground

20

KEY

-

Key

21

n/c

-

Not connected

22

GND

------

Ground

23

/IOW

OUT

Write Strobe

24

GND

------

Ground

25

/IOR

OUT

Read Strobe

26

GND

------

Ground

27

IO_CH_RDY

IN

28

ALE

OUT

Address Latch Enable

29

n/c

-

Not connected

30

GND

------

Ground

31

IRQR

IN

Interrupt Request

32

/IOCS16

?

IO ChipSelect 16

33

DA1

OUT

Address 1

34

n/c

-

Not connected

35

DA0

OUT

Address 0

36

DA2

OUT

Address 2

37

/IDE_CS0

OUT

(1F0-1F7)

38

/IDE_CS1

OUT

(3F6-3F7)

39

/ACTIVE

OUT

Led driver

40

GND

------

Ground

41

+5VL

---->

+5VC (Logic)

42

+5VM

----->

+5VC (Motor)

43

GND

------

Ground

44

/TYPE

----->

Type (0=ATA)

Ribbon Cables (40 versus 80 wire)

80-wire data cables, when used, still only attach to pins 1 to 40. They are part of the UDMA (Ultra DMA) Transfer Mode specification of the ATA/ATAPI-4 standard. The extra wires are interposed between the original 40 wires and all run to earth to prevent stray signals crossing over between adjacent wires. This allows for faster trouble-free data transfer and automatically supports the CableSelect feature. The same standard allows for colour-coding of the connectors on the cable. Blue to motherboard, Grey (in the middle) to any Slave Drive and Black to the Master or to a Single Drive. Under the specification it is not allowable to attach a single drive to the middle connection.